Obstructive sleep apnea (OSA) is characterized by the repetitive closure of the pharyngeal airway during sleep that is associated with oxygen desaturation and/or arousal [87]. Patients with OSA are at increased risk of coronary artery disease, chronic heart failure, hypertension, stroke, type 2 diabetes, and motor vehicle/industrial accidents. With regard to middle-aged adults, approximately 15% of men and 5% of women have mild-to-moderate OSA, and another 9% of men and 4% of women have moderate-to-severe OSA, as de ned by the apnea-hypopnea index (AHI; mean number of apneas and hypopneas per hour of sleep)|mild: 5 ? AHI <15; moderate: 15 ? AHI < 30; and severe: AHI ? 30. OSA is a serious and growing healthcare problem in the U.S. The American Academy of Sleep Medicine (AASM) current practice parameters recommend oral appliance (OA) therapy, such as use of a mandibular advancement appliance (MAA), as a first-line treatment in patients with mild-to-moderate OSA, as well as in patients with more severe OSA who do not have success with positive airway pressure (PAP) therapy. MAAs pull the mandible forward an adjustable amount, reducing the obstruction of the upper airway during sleep. Substantially better results are obtained using MAAs that are custom-made by dentists. Approximately half of patients who attempt PAP therapy cannot tolerate the treatment and prefer an MAA as a less invasive and more portable therapeutic option. Compared to PAP machines, MAAs are also easier to travel with and do not require electrical power; they are a particularly important treatment alternative for individuals with OSA who are employed by the transportation industry (e.g., commercial truck drivers, airline pilots, etc.), whose work often requires them to be away from home. The capability to monitor patient adherence is crucial and is incorporated into essentially all modern PAP units. A major factor limiting wider application of MAA treatment is the present inability to objectively quantify patient adherence to treatment. The need to introduce objective adherence monitoring into OAs is of great importance for both clinical practice and research. The proposed Dental Sentinel will overcome present barriers and offer the capability for adherence monitoring in MAAs and other OAs (e.g., orthodontic retainers). This will put MAAs on the same footing with PAP in this regard, as almost all PAP units electronically record the time that the breathing circuit is pressurized, which is a precise measure of actual usage time. The Dental Sentinel is a miniature adherence and sleep monitoring micro-recorder that is implanted into the OA. It employs temperature, orientation, and motion sensors in a novel way to determine daily use of the OA (i.e., adherence), as well as providing objective measurement of MAA- related improvements in AHI (i.e., treatment ecacy), augmenting subjective patient self reports to clinicians. Monitoring algorithms prevent users from purposely deceiving the device, an important capability to satisfy present and future transportation industry regulatory requirements. The Dental Sentinel will use its recharging console to upload data to a secure cloud-based server, where it can be accessed by authorized individuals.